Who were Ida’s relatives?

Primitive primates – our relatives – are remarkably rare among the fossils in the Messel Pit. This seems like a paradox, since primates would have felt quite at home in the treetops of the humid, warm rain forest which covered this region in the Eocene. Primates were far from rare in Middle Europe 47 million years ago. Why, then, are they rare in Messel?

For a long time, only eight finds of primate fossils were known. These consisted of fragments, small and large – usually either the fore- or hind-part of a skeleton.

The first find

In 1975, a full 100 years after the first fossil finds in Messel, a fossil of a species the size of a housecat was found. It consisted of the hind legs and hip, with grasping feet and a penis bone. Since the forebody was missing, an exact classification of the species was impossible beyond determining that it was most likely a premonkey (Prosimian), related to the lemurs which are only found in Madagascar today (Photo: Wighart von Koenigswald, University of Bonn).

The second find

In 1982 a student discovered the front part of a skull, including its complete set of teeth, which made it possible to positively identify a primate genus from Messel for the first time. It was an Europolemur of an hitherto unknown species, who received the name ”koenigswaldi”. This animal was about half the size of the first find. The distance from the first find and the difference in size meant that the two fossils did not stem from the same individual, but could it be a male and female of the same species? This cannot be completely ruled out, but it is not very probable. In today’s lemurs, the two genders are usually of equal size. Where there is a difference, the male is the smallest. (Photo: Jens L. Franzen, The Senckenberg Institute)

The third find

The third find took place in 1984. It resembles the first, but consists of even smaller fragments and the animal was about 10 % smaller; the penis bone (see arrow) is actually 15 % smaller. It is uncertain whether the two finds represent the same species. (Photo: Wighart von Koenigswald, University of Bonn)

The fourth find

In 1987 came another sensational find, even though it was only a fragment. It consisted of a right forearm, complete with a grasping hand. This is one of the oldest preserved primate hands in existence. The fragment did not include any part of the head, which meant that the teeth were missing and the species could not be determined. However, it is considerably larger than Europolemur koenigswaldi. The fossil was well preserved in three dimensions, topping everything known from the Eocene in Europe up until then. The arm had clearly visible bitemarks from a predator. It may have been a crocodile or an alligator, but this is far from certain. (Photo: S. Tränkner, The Senckenberg Institute)

The fifth find

The fifth find gave scientists a nut to crack. It was found in an area of the quarry which had once been out in the very middle of the lake. How had the fossil arrived there? Deposits around the fossil were fine-grained and would have been carried away if there had been strong currents in the area. The fossil consists of a pair of hind legs and the tail, which is preserved down to the last and most minute joint. The tail vertebrae turned out to have imprints of teeth, and in one of these bitemarks they even found a piece of a tooth. When this turned out to come from a crocodile, it provided a likely explanation of the unusual location of the find: The fossil must be from an animal which was attacked by a crocodile, which then dragged its prey into the deep to devour it there. Based on size, the find is classified as an Europolemur koenigswaldi. Whether it is male or female cannot be determined, since neither a penis bone nor a pelvic bone was found. (Photo: Jens L. Franzen, The Senckenberg Institute)

The sixth find

The next find consists of two parts of a skeleton. One part is comprised of the rib cage, parts of the skull and the upper arms. The other includes the hip and most of the calf and thigh bones. It was found by a private fossil hunter, and bought by The Wyoming Dinosaur Center in USA in 1991. The Center believed they had bought a complete skeleton, but X-ray examinations by Jens Franzen showed that parts of the fossil were faked. It was difficult to determine the species of the fossil, since the only preserved tooth was a damaged piece of a molar. But in the end, scientists were able to determine that this primate must be related to a primate find from Geiseltal, Godinotia neglecta. Certain small irregularities indicated that this fossil might have a more complete counterpart. Even though the fossil was incomplete, it made history. A small, round object in its stomach turned out to come from the core of a fruit, and around it were fragments of various kinds of leaves. What the shape of the teeth of Godinotia neglecta had suggested, was now confirmed: This was a primate who fed on fruits and leaves. (Photo: A. Hebs, The Senckenberg Institute)

The seventh find

This find consists of a lower jaw and a few teeth, but this is sufficient to identify the find as an Europolemur koenigswaldi. Since it was found inside a coprolite (fossil excrement), there is no doubt that the owner of the jaw met a violent death. But which predator might this be? Neither a crocodile nor a predatory bird – their stomach acids would have dissolved the teeth, or at the very least left them obviously and severely damaged. The prime suspect for its size and way of life is the otter-like Buxolestes piscator, who has no living descendants. (Photo: Jens L. Franzen, The Senckenberg Institute)

The eighth find

Up until May 2009, this was the last known primate find from Messel. It is the complete skull of a young animal. The skull and teeth place it in the genus Europolemur. But the size of the skull and some characteristics of the teeth differentiate it from the two previously known species, E. koenigswaldi from Messel and E. klatti from Geiseltal. The new species was given the name E. kelleri. Based on the proportional sizes of these species, there is reason to believe that find # 4 also represents this species. (Photo: Jens L. Franzen, The Senckenberg Institute)

Before Ida, only eight primate fossils had been found in Messel. They were distributed among two genera and three species. All belong to the family Notharctidae, subfamily Cercamoniinae, and the are all only known through fragments. Why is this so, and why are primates so rare among the mammals in Messel?